I. Field of Invention
The present invention relates to a device that warns a pregnant woman when magnetic fields are present that may be harmful to the developing fetus and/or herself.
II. Brief Description of the Prior Art
Recent reports of increased risk of leukemia [Stone, R. Polarized Debate: Emf's, and Cancer. Science, 258:1724-1725, 1992] and other cancers resulting from exposure to electromagnetic radiation have elicited growing public health concern. The human data is reinforced by laboratory in vitro and in vivo studies suggesting changes in normal nocturnal pineal melatonin content [Wilson, B. W., Anderson, L. A., Hilton, D. I. et al. Chronic exposure to 60-Hz electric fields: effects on pineal function in rat. Bioelectromagnetics, 2:371-380, 1981], calcium homeostasis [Bawin, S. M., Adey, W. R., Sensitivity of calcium binding in cerebral tissue to weak environmental electric fields oscillating at low frequency. Proceedings of the National Academy of Science, USA, 73:1999-2003, 1976], and fibroblast protein synthesis [McLeod, K. J., Lee, R. C., Ehrlich, H. P. Frequency dependence of electric field-modulation of fibroblast protein synthesis. Science 236:1456-1469, 1987].
Extremely low frequency electromagnetic fields (in the range of power frequencies; 50-60 Hz) are pervasive in our modern industrialized world, with measurable levels near any appliance powered by electricity. While electric fields are easily shielded to prevent exposure, the magnetic fields resulting from alternating current flows ere much more difficult to diminish by usual barriers. Magnetic fields are created by energized coils, such as those in fans, video display terminals, pencil sharpeners and heaters. At home, motor driven clocks, telephone answering machines on night stands, wall powering adapters, and waterbed and electric blanket heaters could provide exposure to magnetic fields for a significant period of each 24 hour day.
Virtually nothing is known about how magnetic fields affect developing embryos and fetuses. There are numerous physical and chemical agents that are known to alter organ maturation during so-called "vulnerable periods" of development and growth. In view of this fact and the uncertainties over "safe" levels of exposure, avoidance of magnetic fields at home, work and play is believed to be prudent behavior by all pregnant women.
A detection and warning device for developing embryos and fetuses has been previously described by the same inventors in commonly-owned U.S. patent application Ser. No. 08/066,573, filed May 26, 1993, and registered on May 30, 1995, under U.S. Pat. No. 5,420,581 the disclosure of which is hereby incorporated by reference. The device described in U.S. Pat. No. 5,420,581 provided warnings when excessive sound levels were present. It was not designed to detect and warn against magnetic fields.
Although existing magnetic field meters are known that detect magnitudes of magnetic fields of arbitrary orientation, these devices do not present an audible alarm when fields of certain levels are exceeded. Furthermore, existing field meters are not designed to be worn at the abdominal level. Because in situations of practical concern, magnetic fields drop rapidly as the distance between the source of the magnetic field and the target increases, and because the penetration of magnetic fields into the human body is nearly perfect, the level of exposure must be evaluated as close as possible to the target location, in this case the fetus.
It would thus be desirable to have a magnetic field sensor capable of detecting arbitrarily oriented magnetic fields in proximity to a human abdomen and of providing an audible warning when such fields exceed a predetermined level, and to provide such a sensor in a device that is capable of being comfortably carried near the abdomen. Because such a warning device is useful for detecting magnetic fields harmful to a human fetus, it also would be desirable to avoid exposure of the fetus to excessive noise due to the audible alarm.